swap space and dump space configuration

[rollinscf]

I need to verify swap and dump space configurations on a handful of solaris servers. can anyone tell me what the recommeded size is for swap and dump space on solaris servers? i was taught that swap space should be 3x the physical memory of the server but this space seeme like overkill. please let me know your thoughts.

thanks!

 

[elgrandeperro]

Since dump device tends also to be the swap device, the general rule of ~1.5 x memory is what I use. Remember tmpfs also comes from swap, so if you transfer stuff to /tmp, you need to increase.

eugene

 

[Mike042]

Personally, I think it very much depends on the size of memory and whether you are using 'swap space hungry' applications, such as Oracle. I currently use this 'rule of thumb' for our Oracle DB servers where I work, particulary when there is plenty of disk space:

0 - 2 GB Memory, Swapspace = 4 x Memory
2 - 4 GB Memory, Swapspace = 3 x Memory
4 - 8 GB Memory, Swapspace = 2.5 x Memory
8 - 16 GB Memory, Swapspace = 2 x Memory
>= 16 GB Memory, Swapspace = 1 x Memory


I hope that helps.

Mike

 

[dandan123]

Dump space is usually 35% of memory if you are only going to hold kernel pages.

Dump and swap space need not be the same. Having a dedicated dump space is recommended as the crash dump on a common dump/swap device could be overwritten once swap space begins to be used on a reboot.

Also swap can be comprised of multiple disk partitions but you can only have one device dedicated to dump either dedicated or one of the swap devices.

 

[MorganGreylock]

An article I read on sunsolve.sun.com said that they recommend that swap be 30% of physical memory. Having too much swap can reduce performance by causing too many memory pages to get swapped... not sure exactly how that works, it's been too many years since my CS classes, I just know that's what Sun recommends.

 

[dandan123]

There are no thumb rules for swap anymore. It all depends on the applications running on your system.

Where I work most of the servers/zones I handle all run Oracle databases and we usually allocate 100% of memory as swap. These are systems with 128 GB or more of RAM.